Body roll differences in freestyle swimming between swimmers with and without shoulder pain.

Several studies have identified body roll as an important variable that affects shoulder pain due to its potential to modify upper limb kinematics. This study aimed to investigate potential differences in body roll between swimmers with and without shoulder pain. Twenty-four competitive swimmers participated in the study, 12 with unilateral shoulder pain and 12 without. Body roll was measured using two tri-axial accelerometers, one at the shoulder and one at the hip, during three trials of 100 m front crawl swimming at three different speeds. The results showed no significant difference in peak body roll angle between groups for the breathing side at the shoulders or hips. However, for the non-breathing side, swimmers with shoulder pain rolled significantly less at the hips (49º vs 57º, p = 0.018, r = 0.931) while no significant difference was found at the shoulders. These findings suggest that a potential relationship between hip rotation and shoulder pain may exist, such that hip roll is diminished to the non-breathing side in swimmers with unilateral shoulder pain. Given that a cause-effect relationship cannot be inferred from this cross-sectional study, future studies should attempt to identify the mechanisms that link body roll to the aetiology and pathomechanics of shoulder pain.